1. Field of the Invention
The present invention relates, in general, to an electric cooking apparatus and method of controlling heaters thereof and, more particularly, to an electric cooking apparatus and method of controlling heaters thereof, which are capable of uniformly maintaining a temperature of a cooking cavity by cutting off and supplying power to the heaters according to periods preset in view of a temperature of the heaters.
2. Description of the Related Art
Generally, an electric cooking apparatus is provided with electric heaters therein which cook food by heating the food with heat emitted from the electric heaters. The electric cooking apparatus typically includes a cooking cavity to accommodate food, electric heaters to supply heat to the cooking cavity, and a temperature sensor to detect a temperature of the cooking cavity.
Referring to FIGS. 1A and 1B, a conventional method of controlling heaters of the electric cooking apparatus is described below.
In FIG. 1B, an X-axis thereof represents periods, a Y-axis thereof indicates whether power is supplied or not to the heaters. A supply of power to the heaters is indicated by ON, while a cutoff of power to the heaters is indicated by OFF.
In FIG. 1A, an X-axis thereof represents periods, and a Y-axis thereof represents temperatures of the cooking cavity depending on supplies and cutoffs of power to the heaters that are plotted on the lower graph of FIG. 1.
When a cooking mode using the heaters is selected, it is determined whether the temperature of the cooking cavity input from the temperature sensor is higher or lower than a set temperature T1. If the temperature of the cooking cavity is lower than the set temperature T1, the heaters are turned on. Accordingly, the temperature of the cooking cavity increases by operation of the heaters. When the temperature of the cooking cavity increases higher than the set temperature T1 by a certain amount or more (for example, higher than the set temperature T1 by a temperature of +5° C.) (see position A), the power to the heaters is cut off.
When power to the heaters is cut off, the temperature of the cooking cavity slightly increases just after the cutoff of the power. Thereafter, the temperature of the cooking cavity decreases depending on an external temperature or an insulation state of the cooking cavity.
When the temperature of the cooking cavity decreases to less than the set temperature T1 by a certain amount or more (for example, lower than the set temperature T1 by a temperature of −5° C.) (see position B), power is supplied to the heaters again to increase the temperature of the cooking cavity.
When the power is supplied to the heater, the temperature of the cooking cavity increases again. When the temperature of the cooking cavity increases to a level higher than the set temperature T1 by a certain amount or more (see position C), the power to the heaters is cut off to maintain the temperature of the cooking cavity at a temperature near the set temperature T1. The above-described process is repeated during an overall cooking period.
In that case, a power-ON period is longer than a power-OFF period (for example, the power-ON period is twice the power-OFF period), and the power-ON period and the power-OFF period are set in minutes. Accordingly, when the temperature of the heaters is considerably decreased after the power to the heaters had been cut off and several minutes have elapsed, power is supplied to the heaters again.
As described above, the conventional electric cooking apparatus is problematic in that excessive power is consumed to resume a normal operation of the heaters because power is supplied to the heater again after the supply of power to the heater has been cut off and a considerable period has elapsed. Furthermore, the conventional electric cooking apparatus is problematic in that quality of cooking is reduced because the temperature of the cooking cavity is not accurately controlled but roughly controlled, and a cooking period increases because the heat is not uniformly applied to the food.